Features – Tremolo and Reverb
Most vintage amps from the 1950’s and into the 60’s were intended for use for amplifying accordions or Hawaiian lap steel guitars. The concept of a single string guitar lead had not sunk into the music scene very far and was a small part of the business. Guitars were rhythm instruments.
Up until the early 60’s, tremolo was the main effect that amplifiers offered. Tremolo is sometimes called vibrato, but there is much discussion about the true meaning of each term. It is accomplished by adding a circuit that varies the volume of the output at about three or four times a second. You can control the speed of the tremolo and the intensity. It gives you a Hawaiian sound and it can be heard in Surfer guitar music from the late 50’s and early 60’s. It is great for Surfer music and for adding a lush sound to accordion playing, but it doesn’t really sound good with Blues.
Tremolo is an interesting feature in an amp, but you probably won’t use it very often.
Reverb is a more interesting effect. Its goal is to give the music the sound of a large hall with echo effect. It’s like playing in a tile lined Men’s room or a stairwell. Reverb is accomplished by running the sound through a mechanical spring (usually 3 or 4 springs) in a tin can. The amp has a little preamp circuit that drives an actuator at one end of the spring and another preamp that amplifies the output of a pickup at the other end of the spring. The springs vibrate and pass the sound along from one end to the other, but the sound bounces back and forth along the spring making echoes.
Good reverb sounds nice and “wet” and gives body and bass to the sound because the high notes tend to dissipate faster and the low notes build upon themselves. Every Blues Harp player can use just a touch of reverb. Too much reverb is muddy sounding and causes the notes to lose definition.
Reverb was used in the 1950’s mainly for organs; in fact, Hammond manufactured most reverb tanks. Amplifier Mythology says that Linc Ray talked Leo Fender into putting a Hammond reverb tank into a Fender Pro, making it a Fender Pro Reverb.
Most harp players use digital delay instead of reverb, which I think is a mistake. The digital delay can add a reverb-like effect, but a string reverb is its own animal and has a distinct sound. It is much richer and “creamier” sounding.
Tube amp reverb adds the two tube stages to the amplification system that creates opportunity to get a tube driven overdrive. The reverb usually uses an extra 12AX7 tube (often 12AT7) to drive the reverb and capture the sound coming back. (The 12AX7 has two amplifiers in it.)
Tip: A stand-alone tube reverb unit can be an alternative to a tube amp. Just plug the reverb output into the PA and the mic into the unit. You get all the tube distortion you need from the 12AX7 tubes (which are being driven at low voltages – cool sound). The PA makes you loud and provides feedback suppression.